Electric switch actuator having variable movement differential



Oct. 12, 1965 r A, H D 3,211,878

ELECTRIC SWITCH ACTUATOR HAVING VARIABLE MOVEMENT DIFFERENTIAL Filed Jan. 21, 1964 2 Sheets-Sheet l f y E A z q ,/16 Z '11 1?! M is Z i/ zz Q 29, ,q

I v l /ff Oct. 12, 19 5 B. A. HOLDEN ELECTRIC SWITCH ACTUATOR HAVING VARIABLE MOVEMENT DIFFERENTIAL Filed Jan. 21, 1964 2 Sheets-Sheet 2 United States Patent 3,211,878 ELECTRIC SWITCH ACTUATOR HAVING VARI- ABLE MOVEMENT DIFFERENTIAL Brian A. Holden, Newcastle upon Tyne, England, assignor to Burgess Products Companyfimited, Brookfield, England, a company of Great Britain and Northern Ireland Filed Jan. 21, 1964, Ser. No. 339,138 Claims priority, application Great Britain, Jan. 22, 1963,

2,720/ 63 9 Claims. (Cl. 200-472) This invention relates to the actuation of an electric switch of the kind known as a microswitch, wherein the moving contact means are operable by a partially exposed, linearly or angularly displaceable element which for convenience will hereinafter be referred to as a plunger.

In a microswitch, the displacements of the plunger to effect contact change-over in opposite directions or what will hereinafter also for convenience be called operation and release, are constant. Usually, with reference to the unactuated position of the plunger, operation occurs after displacement of the plunger through a part of what may be called its depression, the remainder thereof being overtravel, while release occurs after displacement of the plunger through a major part of its return movement towards said unactuated position. At operation the plunger is further depressed than at release; the diiference between these two degrees of depression is known as movement differential.

In process control applications, microswitches are frequently arranged to be actuated by means responsive to a given physical condition, such as a thermostat or a pressure sensitive device. The change of form of such responsive means is usually linear, and it usually exerts a force much greater than either the force required to operate the switch, or the force exerted by the switch on its plunger during release. It follows that when such a responsive means is arranged to bear directly upon the switch plunger, operation and release of the switch depend invariably upon said change of form of the responsive means, or are effected at invariably related values of the governing physical condition. In other words, since the movement differential of the switch plunger is fixed, the difference of temperature, pressure or other physical condition at which the switch is operated and released is likewise fixed.

For the understanding of the invention, it is also to be stated that the value of the actuating force required to operate a microswitch is greater than the value of said force at which the switch will effect its own release, and the difference between these two values is known as the force differential. 7

An object of the invention is to provide for a microswitch as above discussed, an actuator affording a variable movement differential.

For the attainment of this object, the invention provides an actuator comprising an element supported to engage the switch plunger, a lever mounted on said element to be angularly displaceable relative thereto and adapted to be borne upon by a physically responsive means, resilient means disposed to apply, in opposition to displacement of said lever by said responsive means, a resistive force within the force differential of the switch, and stop means adjustable for variably limiting the displacement of said lever by said responsive means.

An actuator according to the invention may be supported in or on a casing or bracket securable to the body of the microswitch by the usual screws or rivets with which said body is positioned. The casing or bracket may afford guide means or mounting means for a dis- 3,211,878 Patented Oct. 12, 1965 ice placer element, which for convenience will be called a push-button, located to bear upon said lever and to have applied to it a controlling operation of responsive means.

Alternatively, when the body of a switch in known manner comprises a casing enclosing the switch mechanism and a lid which closes one open side of said casing and affords a mounting for the aforesaid plunger, actuating means according to the invention may be applied to a switch of this kind by modifying said lid to provide a support for said element engaging the switch plunger and guidably accommodate the actuator means, said push-button then being fixed in said lever.

Said push-button is preferably arranged to bear upon the lever, or is fixed in the lever, at a smaller distance from the lever pivot than said stop means. This permits the adjustability of the stop means to be coarse relative to the fine tolerances permissible in the actuator; for example, the stop means may comprise a screw having 40 threads per inch.

The resilient means in the actuator may also be adjustable, since the force differential of individual microswitches, even when of the same type, may vary, and it is necessary that the resistive force of the spring shall be less than the switch operating force (e.g. 10 ounces) and greater than the switch release force (e.g. 6 ounces). Preferably, said resilient means is such that it is adjustable as a production operation in relation to a particular switch whereto the actuator is secured, the resilient means then being fixed in its adjusted position, leaving only the stop means adjustable at the point of use to afford the required movement differential of the actuator pushbutton, which may differ to a greater or less extent from the movement differential of the switch plunger as will hereinafter be referred to.

Advantageously, the supported element of the actuator may be pivotally supported by one end in or on said casing or bracket, or in a lid member of the switch body, and may bear at a point adjacent its other end upon the switch plunger. Said element may carry adjacent its pivot a threaded stud which passes through a hole or recess adjacent the end of a longer arm of the lever, and is engaged by a nut serving as said adjustable stop means, the shorter arm of said lever being borne upon by or having fixed in it said push-button, for example, in substantial alignment with the switch plunger.

Said supported element may be made of laminar metal,

'and the lever may be made of relatively thicker metal strip. Either of such element and lever may support a member formed to be slidable thereon and having a spring tongue bearing upon the other as the aforesaid resilient means; the adjustment of said resilient means may be effected by sliding the spring tongue member lengthwise thereon, and thereafter securing it, for example by spot-soldering or spot-welding.

In order that the invention may be better understood embodiments thereof will be briefly described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 shows an actuator in longitudinal section applied to the body of a microswitch M the internal contacts of which are actuable by a plunger P,

FIG. 2 shows in longitudinal section a similar arrangement of an actuator applied to a lid of a switch body,

FIGS. 3 and 4 are sections on the lines IIIIII and IV-IV respectively of FIG. 2, and

FIG. 5 is a perspective view, on a larger scale, of a resilient member included in the actuator.

Referring now to FIG. 1, the actuator is housed in a casing 11 which is securable to the switch body by screws or rivets passing through holes H in said body, whereby the switch is positioned.

The supported element of the actuator is an arm in the form of a channel section pressing 12 of relatively thin sheet metal which is pivoted adjacent one end of a pin 13 transversely located in the casing 11, and bears at a point adjacent its other end on the switch plunger P. For mounting on the pin 13, the element 12 is provided with a pair of D-form apertures 14 extending up its side walls 15, and in the middle of its base with a boss 16, so that without the need for drilling holes the element 12 can be mounted on the pin 13 without play. Nearer its end which bears upon the switch plunger, there is formed from the base of the element 12 an inwardly and obliquely extending tongue 17 having two lateral shoulders, the surfaces of which are indicated at 18, to provide support with transverse line contact for a lever member 19 which lies within the channel element 12 and is made of a strip of relatively thicker metal so as to be, for practical purposes, within the requirements of the actuator, substantially rigid. This lever 19 has a transverse slot 20 through which the tongue 17 passes, the edges of the lateral shoulders 18 bearing on the surface of the lever adjacent the base of the element 12, on either side of said slot 20. Further, at the end of the element 12 which bears on the switch plunger, the side walls 15 of said element have extensions 21 which extend over lateral projections at the corresponding end of the lever 19, the inner limits of said projections being indicated by dotted lines 22. Adjacent the same end, the lever 19 is contacted by the inner end of a push-button 23 mounted in an aperture 24 in the casing 11, and having internally a collar 25 whereby it is retained in said casing.

Adjacent the pivoted end of the element 12 there is mounted in the base, within the channel form of said element, a screw-threaded stud 26 which passes freely through a slot 27 in the corresponding end of the lever 19. Engaged on the stud 26 is a nut 28 the end of which is accessible for rotation, preferably by a special key, through a hole 29 in the casing 11.

The channel section member 12 also carries an element comprising a spring tongue 30 which is an integral projection from the base 31 of a channel section clip, said base 31 extending across the open side of the channel element 12 and its limbs which embrace the walls 15 of said channel element having at their free ends inwardly turned lips 32 which engage beneath the base of said channel element 12 so that the member 31 is slidably secured upon said element 12, with the tongue 30 bearing resiliently on the longer arm of the lever 19 in opposition to the pushbutton 23 which bears upon the shorter arm.

In the embodiment illustrated in FIGS. 2-5 components of the actuator having the same functions as those included in FIG. 1 are indicated by the same reference numerals, although they may be slightly modified in form.

In this embodiment the actuator is mounted on a modified lid L secured to the open side of a casing C which contains the mechanism of a microswitch, the lid L having an aperture in which the plunger P is slidable.

The lid L is generally of channel-section, having two upstanding walls 33 which have adjacent one end coaxial apertures for the mounting of the pin 13. On this pin there is pivotally mounted in the manner described above a channel-section element 12, of which the end remote from the pin bears on the switch plunger P, and the other end, adjacent the pin, has a downwardly bent tongue 34 which can engage the base surface of the channel in the lid and so limit outward displacement of the plunger P.

The element 12 has an upwardly turned tongue 37, which differs from the tongue 17 shown in FIG. 1 in being turned at right angles to the base of the element 12, although as shown in FIG. 4 this tongue likewise has lateral shoulders 18 upon which the lever 19 rests. A pushbutton 43 intended to be engaged by external responsive means is fixed in one end of the lever 19 over the switch plunger P, and the other end of the lever 19 is forked to provide a recess 47 in which the screw-threaded stud 26 is located. The stud 26, as before, carries a nut 28 by which the maximum displacement of the lever 19 relative to the element 12 is regulated.

There is mounted about the channel-form element 12 a resilient member comprising a spring tongue 30 which bears upon the lever 19 so as to oppose any force exerted on said lever by pressure upon the push-button 43, this tongue extending, as more particularly shown in FIG. 5, from the base 31 of a clip which is rectangular in section, the clip being slidable lengthwise upon the member 12 and held in position by a pair of lips 32 which engage beneath the base of said member 12.

Evidently, the arrangement illustrated in FIGS. 2-5 can be easily assembled when the spring tongue 30 is moved by sliding towards the pivoted end of the member 12. The lever 19 can be slid endwise over the top of the tongue 37 until the recess 47 embraces the stud 26, and the tongue 37 enters the hole 40 in said lever. The assembly is located in the channel presented by the lid L, and pivotally mounted by insertion of the pin 13. It is then only required to adjust the location of the spring tongue 30 by sliding the clip to a position such that, upon an experimental pressure being applied to the push-button 43, the tongue 30 will yield and permit the forked end of the lever 19 to rise into engagement with the nut 28 before said pressure causes the plunger P of the switch to be depressed, while upon gradual relief of said force upon the push-button 43 the lever 19 is caused by the spring to move so as to separate its forked end from the nut 28 before the internal resilient means of the switch causes the plunger P to displace the element 12.

In the operation of either embodiment of the actuator as described, when no force is applied to the push-button 23 (FIG. 1) or 43 (FIG. 2) the spring tongue 30 displaces the longer arm of the lever 19 away from the nut 28 and into engagement with the inner surface of the base of the element 12 (FIG. 1) or with the flange 46 on stud 26 (FIG. 2). When a force is applied to displace the push-button 23 or 43, for example, by a thermostat, while the element 12 is held by the operating force of the plunger P, the spring tongue 30 yields so that the lever 19 is displaced until its longer arm engages the nut 28, whereafter the element 12 depresses the switch plunger P so as to effect operation of the switch. Since the abutment of said longer arm of said lever 19 against the nut 28, as shown in the drawings, is the limit of lost motion in the actuator, further movement of the pushbutton 23 must depress the plunger P and operate the switch.

Evidently, the permitted displacement of the push-button 23 before operation of the switch is controlled by the adjustment of the nut 28, so that the point at which the switch is operated by the displacement of a responsive means such as a thermostat can be varied to a considerable extent.

On the other hand, in the course of release of the switch by retraction of said responsive means, the point of release is constant. Since the force applied to the lever 19 by the spring 30 is greater than the release pressure of the switch, when withdrawal of the push-button 23 is permitted by the responsive means, the first movement which occurs is displacement of the longer arm of the lever 19 from engagement with the nut 28 to engagement with the inner surface of the base of the element 12. The shorter arm of said lever and the element 12 itself are then displaced by the switch plunger until the latter reaches the degree of projection from the switch body at which release of the switch occurs.

Since the actuator thus affords a constant release position with a variable operating position of the push-button 23, the actuator evidently affords a variable movement differential which can be regulated according to requirement of the users control system by adjustment of the nut 28.

The arrangement of either embodiment of the actuator as illustrated in the drawings is also adjustable as a production step, so as to ensure that the force applied by the spring tongue 30 to the lever 19 is less than the operating pressure of the switch plunger P but greater than the release pressure thereof, by sliding the clip 31-32 from which the tongue 30 extends lengthwise upon the element 12. When a suitably adjusted position has been attained the clip can be permanently secured in this position, for example, by a minute spot-weld which posi tively secures it against further displacement on said element 12. t .g

The illustration and foregoing description of actu tors according to the invention have been given solely by way of example, and to indicate modes of construction wherein each of the three elements 12, 19 and 30-32 is a pressing from sheet metal. This while eliminating machining, nevertheless provides an actuator assembly the dimensions of which may be controlled within suitable tolerances. It will be understood that for clarity of illustration the actuators are shown in the drawings on a greatly enlarged scale. In practice, the length of the switch body M (FIG. 1) may be approximately 25 mm. while the length of the lid L (FIG. 2) may be about 40-50 mm., the various components of the actuator having proportionate dimensions.

What I claim and desire to secure by Letters Patent is:

1. The combination, with a micro-switch of the kind having a plunger biased within the switch to be capable of depression by a predetermined operating force and thereafter to exert a lesser release force, of actuator means comprising an arm in continuous engagement adjacent one of its ends with said plunger, a pivotal support for said arm adjacent its other end, a lever mounted on said arm to be angularly displaceable relative thereto about an axis parallel to said pivotal support and adapted to be borne upon by a physically responsive means, resilient means disposed to apply, in opposition to displacement of said lever by said responsive means, a resistive force less than said operating force and greater than said release force, .and stop means mounted on said arm and adjustable for variably limiting displacement of said lever relative to said arm.

2. The combination of micro-switch and actuator means as claimed in claim 1, wherein said arm has a channel section within which said lever is located, and said resilient means comprises a channel section clip slidable longitudinally upon said arm with the base of said clip extending across the open side of the channel section of said arm, the clip having lips which engage beneath the base of said arm and a spring tongue projecting integrally from the base of said clip to bear resiliently on said lever between the pivotal axis thereof and said stop means.

3. The combination of micro-switch and actuator means as claimed in claim 1, wherein said micro-switch has a body provided with holes for elements whereby said body is mountable, and further comprising, a supporting member which provides said pivotal support for said arm and is securable to said body by means passed through said holes.

4. The combination of micro-switch and actuator means as claimed in claim 3, further comprising a push button slidably mounted in said supporting member to bear upon said lever.

5. The combination of micro-switch and actuator means as claimed in claim 4, wherein said push button is located to bear upon one arm of said lever at a smaller distance from said pivotal axis thereof than the distance from said pivotal axis to said stop means.

6. The combination of micro-switch and actuator means as claimed in claim 4, wherein said supporting member is of box form to enclose the actuator means and has an aperture through which said stop means is accessible for adjustment, and wherein further said arm has a channel section within which said lever is located, and said resilient means comprises a channel section clip slidable longitudinally upon said arm with the base of said clip extending across the open side of the channel section of said arm, the clip having lips which engage beneath the base of said arm and a spring tongue projecting integrally from the base of said clip to bear resiliently on said lever between the pivotal axis thereof and said stop means.

7. The combination of micro-switch and actuator means as claimed in claim 1, wherein the micro-switch has a body which comprises a casing enclosing the switch mechanism and a lid which closes an open side of the casing and affords a mounting for said plunger, said lid having walls wherein is mounted a pin constituting said pivotal support of said arm engaging the plunger.

8. The combination of micro-switch and actuator means as claimed in claim 7, having a push button fixed in one arm of said lever at a smaller distance from said pivotal axis thereof than the distance from said pivotal axis to said stop means.

9. The combination of micro-switch and actuator means as claimed in claim 7, wherein said arm has a channel section within which said lever is located, and said resilient means comprises a channel section clip slidable longitudinally upon said arm with the base of said clip extending across the open side of the channel section of said arm, the clip having lips which engage beneath the base of said arm and a spring tongue projecting integrally from the base of said clip to bear resiliently on said lever between the pivotal axis thereof and said stop means.

References Cited by the Examiner UNITED STATES PATENTS 2,511,271 6/50 Kaminky et al. 200l72 KATHLEEN H. CLAFFY, Primary Examiner.

BERNARD A. GILHEANY, Examiner. 

1. THE COMBINATION, WITH A MICRO-SWITCH OF THE KIND HAVING A PLUNGER BIASED WITHIN THE SWITCH TO BE CAPABLE OF DEPRESSION BY A PREDETERMINED OPERATING FORCE AND THEREAFTER TO EXERT A LESSER RELEASE FORCE, OF ACTUATOR MEANS COMPRISING AN ARM IN CONTINUOUS ENGAGEMENT ADJACENT ONE OF ITS ENDS WITH SAID PLUNGER, A PIVOTAL SUPPORT FOR SAID ARM ADJACENT ITS OTHER END, A LEVER MOUNTED ON SAID ARM TO BE ANGULARLY DISPLACEABLE RELATIVE THERETO ABOUT AN AXIS PARALLEL TO SAID PIVOTAL SUPPORT AND ADAPTED TO BE BORNE UPON BY A PHYSICALLY RESPONSIVE MEANS, RESILIENT MEANS DISPOSED BY APPLY, IN OPPOSITION TO DISPLACEMENT OF SAID LEVER BY SAID RESPONSIVE MEANS, A RESISTIVE FORCE LESS THAN SAID OPERATING FORCE AND GREATER THAN SAID RELEASE FORCE, AND STOP MEANS MOUNTED ON SAID ARM AND ADJUSTING FOR VARIABLY LIMITING DISPLACEMENT OF SAID LEVER RELATIVE TO SAID ARM. 